1. Field of the Invention
The present invention relates to a zoom lens mount assembly for use in optical apparatus such as photographic camera, handy movie camera, video camera, copying machine or enlarger.
2. Prior Art
The zoom lens mount assembly generally comprises a cam sleeve having elongate cam tracks extending circumferentially therearound and movable sleeves having fixed cam followers extending through the cam tracks and movably supported inside the cam sleeve to carry magnification-variable lenses as well as compensation lenses so that the respective movable sleeves may be moved in parallel to the optical axis by rotationally driving the cam sleeve to achieve a desired variable magnification.
Specifically, there is provided the cam sleeve stationarily in the direction of the optical axis but rotatably around its own axis and a plurality of movable frames are provided inside the cam sleeve so that the respective movable frames are guided by the cam sleeve and thereby moved along the optical axis in operative association with the cam sleeve as the latter is rotated around its own axis.
The zoom lens mount assembly of this type often includes a movable frame carrying a focussing optical system so arranged that this movable frame may be driven by drive means provided separately of the drive means for the cam sleeve to achieve the focussing control. One example of such well known zoom lens mount assembly contains therein a program lens shutter having shutter blades serving also as an iris diaphragm.
The zoom lens mount assembly of prior art as mentioned above has inevitably encountered first through fourth problems as follows: